1. Field of the Invention
The present invention relates to a micro device and a method of manufacturing the same. More particularly, the invention relates to a method of manufacturing an ink-jet printing head wherein a part of a pressure generating chamber communicating with a nozzle aperture for ejecting ink droplets is composed of a diaphragm, a piezoelectric element is provided via the diaphragm and an ink droplet is ejected by the displacement of the piezoelectric element, the ink-jet printing head and an ink-jet printing device.
2. Related Art
Heretofore, there is an ink-jet printing head so manufactured as one type of a micro device including such an ink-jet printing head provided with an active plate and an active plate actuator for driving the active plate on one side of a substrate.
There has been known two different types of such an ink-jet printing head in which a part of a pressure generating chamber communicating with a nozzle aperture for ejecting ink droplets is composed of a diaphragm, an ink droplet is ejected from a nozzle aperture by deforming the diaphragm by a piezoelectric element and pressurizing ink in the pressure generating chamber. One type employs a piezoelectric actuator in a longitudinal vibration mode in which the piezoelectric element expands and contracts in an axial direction, whereas the other type includes a piezoelectric actuator in a flexural vibration mode.
For the former type, the volume of a pressure generating chamber can vary by contacting an end face of the piezoelectric element to a diaphragm and a head suitable for high density printing can be manufactured. However, this type requires a difficult process for cutting into piezoelectric elements according to the arrangement pitch of nozzle apertures like the teeth of a comb and work for positioning and fixing the cut piezoelectric element on a pressure generating chamber. Thus, this type of the printing head requires a complicated manufacturing process.
In the meantime, for the latter type, a piezoelectric element can be attached onto a diaphragm in a relatively simple process for sticking and burning a green sheet serving as a piezoelectric material so that the shape is in the shape of a pressure generating chamber. However, a certain area is required because flexural vibration is utilized and, hence, there would it is difficult to form high density arrangement.
To solve the problems of the printing head equivalent to the latter type, a printing head wherein a uniform piezoelectric material layer is formed overall on the surface of a diaphragm using film forming technique, the piezoelectric material layer is cut into a shape corresponding to a pressure generating chamber by lithography and a piezoelectric element is independently formed for every pressure generating chamber is proposed as disclosed in Unexamined Japanese Patent Publication No. Hei. 5-286131.
Hereby, there are advantages for not demanding work for sticking a piezoelectric element on a diaphragm and a piezoelectric element can be fixed by a precise, simple method of lithography. In addition, a piezoelectric element can be thinned that enables high speed driving.
In this case, a monocrystalline silicon substrate, for example, can be used for a substrate, a pressure generating chamber and a passage such as a reservoir can be formed by anisotropic etching and recording density can be enhanced by reducing the area of the opening of a pressure generating chamber as much as possible.
When the above monocrystalline silicon substrate is anisotropically etched, parts to be through holes such as a reference hole for positioning, an ink inlet and a separating hole every are formed simultaneously with pressure generating chambers. At this time, generally, after the monocrystalline silicon substrate, except a silicon dioxide film which is the lowest layer, is etched, a part of a film corresponding to a through hole is etched or removed physically. However, there is a problem that when the films are removed, surroundings of the through hole are overetched or films around the through hole are peeled. If only the silicon dioxide film is left, there is a problem that etching gas or etchant invades on the reverse side due to the defect of the film. Further, particularly if a part of the films corresponding to a through hole are physically removed by inserting a reference pin and others, there is a problem that a film is freed, invades between the reference pin and the through hole and the failure of alignment is caused.
Such problems are caused not only in an ink-jet printing head but in a micro device such as a micro sensor provided with an active plate and an active plate actuator on one side of a substrate.